We are continuing the study of pathogenesis in V. cholerae, with an emphasis of events occurring in intact animals. Mutants which give reduced diarrheal responses are being characterized and genetically mapped. The types of mutants under study include motility mutants, chemotaxis mutants, protease mutants, neuraminidase mutants, toxin mutants, mucin-non degrading mutants, and mutants of unspecified phanotype. Possible vaccine strains are being evaluated.